Photosensitive layers of electrophotographic photosensitive members used in electrophotographic apparatus are known to include a single-layer type photosensitive layer and a multi-layer type photosensitive layer. The electrophotographic photosensitive members are also roughly grouped into a positive-chargeable electrophotographic photosensitive member and a negative-chargeable electrophotographic photosensitive member, depending on the polarity of electric charges produced when their surfaces are electrostatically charged. Of these, a negative-chargeable electrophotographic photosensitive member having a multi-layer type photosensitive layer is commonly used.
The negative-chargeable electrophotographic photosensitive member having a multi-layer type photosensitive layer commonly has on a support a charge generation layer containing a charge-generating material such as an azo pigment or a phthalocyanine pigment and a hole transport layer containing a hole-transporting material such as a hydrazone compound, a triarylamine compound or a stilbene compound which are in this order from the support side.
However, where the photosensitive layer (in particular, the charge generation layer in the case of the multi-layer type photosensitive layer) is directly provided on the support, it may often come about that the photosensitive layer (charge generation layer) comes to peel or that any defects (shape-related defects such as scratches or material-related defects such as impurities) of the surface of the support are directly reflected on images to cause problems such as black dot-like image defects and blank areas.
To resolve these problems, most electrophotographic photosensitive members are provided with a layer called an intermediate layer (also called a subbing layer) between the photosensitive layer and the support.
However, such electrophotographic photosensitive members are seen in some cases to become poor in electrophotographic performance as being presumably due to the intermediate layer. Accordingly, it has conventionally been attempted to improve properties of the intermediate layer by using various means, e.g., by incorporating the intermediate layer of the negative-chargeable electrophotographic photosensitive member with an electron-transporting material to make the intermediate layer into an electron-transport layer (Japanese Patent Applications Laid-open No. 2001-83726 and No. 2003-345044).